Container closure



p 1968 M. M. STERNAU 3,402,874

CONTAINER CLOSURE I Filed May 12, 1964 5 Sheets-Sheet 1 I I l A L IINVENTOR; MARTIN M. STERNAU HwlDmAfyBaw ATTORNEY Sept. 24, 1968 M. M.STERNAU CONTAINER CLOSURE 5 Sheets-Sheet 2 Filed May 12, 1964 FIG. 7A

uvmvro x MARTIN M. STERNAU Hamil, WW P m ATTORNEY p 24, 1968 M. M.STERNAU 3,402,874

CONTAINER CLOSURE Filed May 12, 1964 5 Sheets-Sheet 3 F/GJZ IN VEN TOR.MARTIN M. STERNAU HMLm/a ym ATTORNEY Sept. 24, 1968 M. M. STERNAUCONTAINER CLOSURE 5 Sheets-Sheet 4 Filed May 12, 1964 FIE/3 INVENTOR.MARTIN M. STERNAU P 1968 M. M. STERNAU CONTAINER CLOSURE 5 Sheets-Sheet5 Filed May 12, 1964 IINVENTOR. MARTIN M. STERNAU United States Patent 03,402,874 CONTAINER CLOSURE Martin M. Sternau, Flushing, N.Y., assignor,by direct and mesne assignments, to W. R. Grace & 01., Duncan, SC, acorporation of Connecticut Continuation-impart of applications Ser. No.591,628, June 15, 1956, and Ser. No. 653,227, Apr. 16, 1957. Thisapplication May 12, 1964, Ser. No. 366,784

10 Claims. (Cl. 22943) This invention relates to the packaging art andmore particularly to container closures.

This application is a continuation-in-part of my copending applicationsSerial No. 591,628 filed June 15, 1956, now Patent Number 3,348,358 andSerial No. 653,- 227 filed April 16, 1957, and now abandoned.

In general, the types of containers with which the inventive principlesmay be most readily and advantageously utilized are open mouthcontainers, the open mouth being defined by an enclosing rim formed, inmany instances, by a beaded 0r enlarged lip. Such containers have avariety of cross-sectional configurations and shapes, and are frequentlymade out of paper, plastic, metal, etc. The containers are commonlyutilized to package a variety of foodstuffs such as, for example, fruit,vegetables, meat, candy, bakery goods, and similar items.

In order to close such containers, specially designed closures in theform of lids, covers, caps, etc., have previously been provided.Generally, such closures have been made of relatively rigid thickmaterials preformed into a desired shape and size for subsequentapplication to the containers by association with the rim structure ofthe container.

Frequently, the container structure has been provided with specialgrooves, ribs, slots, embossments, and the like, in the rim area forassociation with the closure to properly hold the closure on thecontainer and seal the container. It will be appreciated that thenecessity for special closure receiving portions on the containersincreases the overall size of the container required to package a givenamount of goods and the amount of material required to fabricate thecontainers. Furthermore, the container cavity cannot be completelyfilled to the top of the rim since the contents must be spaced below therim a sufficient distance to permit subsequent association of theclosure with the container.

Oftentimes closures of the type to which this invention relates haverequired the application of a considerable amount of force forassociation with the container. Consequently, the containers must bemade sufliciently rigid to withstand the assembly forces therebyimposing additional limitations on the container and the goods which maybe packaged therein. Similarly, for example, in the packaging ofoverstufied containers care must be exercised to prevent damage to suchcontents as soft fresh fruit, or the like, which is easily crushed orbruised.

Closures of the type previously referred to often require ratherelaborate assembly equipment as well as separate manufacturing equipmentthus greatly increasing packaging costs. Furthermore, the closurematerial and closures must be handled and stored several times.Consequently, sanitation problems are increased and the closures aresubjected to damage and contamination each time they are handled priorto application to the container.

Those skilled in the art of packaging foodstuifs, particularly frozenfoodstuffs, freshly baked bakery goods, freshly picked fruit, and thelike, will recognize the desirability of closure means which can beformed from basic raw material directly on the container immediatelyafter the goods are placed in the container Without requiring elaborateforming equipment or sanitary precautions.

I have discovered that the class of materials commonly 3,402,874Patented Sept. 24, 1968 identified as oriented heat shrinkable polymersare particularly well suited for the manufacture of such closures.Whereas, in the prior art, it has been suggested that closures be formedfrom shrinkable material, for special applications by rather elaborateequipment, I have discovered that film in the class of materials knownas oriented heat shrinkable polymer film can be utilized to formclosures directly on a container by relatively simple proceduresutilizing relatively simple apparatus. Although the broadest aspects ofthe invention include the use of film material or perhaps even thickersheet material, I have surprisingly found thin film to be of particularutility and far more advantageous in many applications.

This invention is to be clearly distinguished from the well known priorart practices relating to the formation of tamper proof bottle seals andthe like. Prior art of this general type, as shown by United StatesPatent 2,151,508, is directed to the problem of providing a band orouter cover of material around a removable and replaceable bottle cap orcork so that the bottle can be opened only by mutilating the materialthus preventing unknowledgeable tampering with the contents. In otherWords, in the prior art, tamper proof seals have been provided in addition to a separate closure for sealing and holding the contents of thebottle. On the other hand, this invention is directed specifically tothe provision of closures which in and of themselves seal the containerwith which they are associated and hold the goods therein.

Another type of prior art packaging practice from which the presentinvention is to be clearly distinguished is the encapsulation ofarticles by use of shrinkable materials which extend completely aroundthe goods to be packaged in surface to surface engagement therewith toform the complete package as disclosed, for example, in United StatesPatent 2,168,651. Such packages are generally formed by heat sealingoverlapping portions of the material and then applying heat uniformly tothe entire package.

Still another typeof prior art practice from which the present inventionis clearly distinguishable is the formation of thick strong rigid bottlecaps or the like which require the use of materials having particularlyhigh strength characteristics because of the nature of the contents ofsuch bottles and their use. For example, the formation of bottle capsfor bottling beer and carbonated soft drinks requires entirely ditferentconsiderations than in the packaging of foodstuffs and the like aspreviously described. In such prior art practices and others, the cap ispreformed and then applied to the container as shown, for example, byUnited States Patent 2,608,334.

While heat for shrinkage may be applied in a variety of ways, includingelectrical conduction apparatus, in the broader aspects of theinvention, I have further discovered that the general class of materialsknown as oriented heat shrinkable polymers are particularly well suitedto the formation of closures on the container solely by utilization of afluid such as air at an elevated temperature to apply heat byconvection. Such a fluid may be selectively applied dynamically indiscrete quantities by a hot air blower, or the like, or may be appliedstatically by a surrounding fluid environment at an elevated temperaturesufiiciently high to cause shrinkage of the material to form theclosure. In'accordance with my invention, unformed sheets of theoriented heat shrinkable polymer film material can be used to formclosures on containers by the simple expedient of positioning thematerial over the mouth of the container and applying heat thereto whichcauses shrinkage of the material and conformation to the rim structureof the container. A piece of oriented heat shrinkable polymer filmmaterial supported on the rim of a container will tend to conform to theshape of the rim of the container when shrunk. It may be readilyappreciated that these concepts lend themselves to the development ofmethods and apparatus for forming closures having a simplicityheretofore unknown and at a cost heretofore unattainable.

It will appear to the man of ordinary skill in the packaging art thatthe formation of a closure by the simple expedient of exposing orientedheat shrinkable polymer film material to a hightemperature environmentwill likely. result in merely a shriveled piece of film material ratherthan the formation of a useful closure. An obvious apparent solutionmight be to follow certain prior art teachings and utilize ratherelaborate forming equipment to obtain a preselected preformed shapeprior to the application of heat. However, many of the aforementionedproblems would not be overcome and many of the aforementioned advantageswould be lost. Surprisingly enough, I have discovered that closures maybe formed by relatively simple apparatus through the use of a techniquewhich I refer to as selective shrinkage. By utilizing selectiveshrinkage I have manufactured effective closures for containers bysimply placing a sheet of unformed oriented heat shrinkable polymer filmover a container, holding the unformed film only on the rim of thecontainer, and applying heat to the film at the rim to cause shrinkageof the film at the rim. I have found that I can produce closures by thismethod which will create a seal at the rim of the container sufficientto hold water in the container without leakage for an extended period oftime.

It will be readily appreciated by those skilled in the packaging artthat the formation of closures by my heat shrinkage techniques lendsitself to mass packaging procedures to a far greater extent than any ofthe prior art methods and apparatus. The prior art methods and apparatustypically contemplate the utilization of a separate forming head foreach closure to be manufactured. Such forming heads often comprise a diearrangement which is used to preform the closure material into thegeneral shape desired. In many prior applications, the heat utilized inthe formation of the closures by heat sealing as well as heat shrinkagehas commonly been provided by electrical coils or the like imbedded inassociated die structure and adapted to transfer the heat to the closurematerial by conduction through the dies. Utilization of my inventionwill enable the formation of closures on a mass production basis by suchsimple expedients as merely passing containers With pieces of unformedfilm closure material positioned on the container rim through ovens orthe like wherein the ambient temperature is maintained sufficiently highto cause shrinkage of the oriented heat shrinkable polymer film materialand simultaneous formation of a closure and seal on the container.

In order to illustrate the many possible uses of my inventiveprinciples, I have hereinafter disclosed various types of closures andvarious methods of manufacturing the closures all of which embody themore generic concepts hereinbefore outlined.

' One of the objects of my invention is to provide a onepiece closure ofthe type hereinbefore described which is inexpensive and provides asimple hermetic seal for a container irrespective of whether thecontainer is made of paper, plastic, aluminum, steel, etc.

Another object of my invention is to provide a multiplepart closurewhich illustratively comprises an inner layer of closure material forsealing and a separate outer protective layer of closure material.

In other words, the principles of my invention may be utilized tomanufacture a closure from transparent oriented plastic material alone,or from two dissimilar materials with the inner component being formedof the transparent oriented plastic material and the outer componentbeing formed of a semi-rigid moldable material, for example.

Another object of my invention is to provide a sealing closure that willpermit removal and replacement. Such an arrangement also may be utilizedwith a two-part closure so that the outer cover may be'removed forinspection of the contents of the container without removal of the innercover and without breaking the seal provided thereby sothat danger ofcontamination will be eliminated.

Another object of my invention is to provide a multiplepart closure,which may be a two-part closure or a threepart closure, with an innerstiffening component associated with an outer sealing component with orwithout further protective covering. 7

While a primary object of the present invention is. to provide new andimproved container closure means, other related objects areto provide: acontainer closure manufactured from oriented heat shrinkable polymerfilm material; new and improved container closure means comprising aplurality of components at least one of which is made of oriented heatshrinkable polymer film material; a container closure manufactured fromoriented heat shrinkable polymer film material and having meansassociated therewith to facilitate opening of the closure; a new andimproved closure which has an elastic rim or edge and is removable andreappliable; a new and improved closure comprising a plurality ofcomponents at least one of which is made from transparent oriented heatshrinkable polymer film material and at least one of which provideswindow means through which goods in a container may be viewed throughthe transparent ma terial; and a closure made from oriented heatshrinkable polymer film material having container bracing meansintegrally associated therewith.

Another primary object of the present invention is to provide new andimproved methods of manufacturing a closure for a container and otherrelated objects are to provide new and improved methods of: forming aclosure on a container; manufacturing a hermetically sealing cover frombasic raw sheet (i.e. unformed) materials directly upon the containerupon which it is used and at the time of closure of the container (i.e.simultaneously with the formation of the closure from the unformed rawstock by heat shrinkage) while using the container as a male formingcomponent for the closure; forming a closure from unformed oriented heatshrinkable polymer film material solely by direct application of heat tothe material by a fluid medium; forming a closure from unformed orientedheat shrinkable polymer film material by selective shrinkage; andforming a closure from unformed oriented heat shrinkable polymer filmmaterial directly on a container by application of heat through a fluidmedium in a manner causing selective shrinkage at the rim area of thecontainer resulting in the formation of a closure solely by shrinkage ofthe material onto the rim of the container.

Another primary object of the present invention is to provide new andimproved apparatus for manufacturing a closure for a container and otherrelated objects are to provide new and improved apparatus for:supporting unformed oriented heat shrinkable polymer film material priorto association with a container; applying the material to a container;holding the material on the container; and selectively applying heat tothe material on the container to form a closure thereon.

In general, any of the known oriented heat shrinkable polymer materialsmay be utilized, to a greater or lesser degree, in my invention. Theselection and use of the proper type of material will vary fromapplication to application depending upon availability, the particularpack-.

aging problem, and the personal preferences of the particular packager.Various packaging applications may requir e variations in the physicalcharacteristics of the closure material thus making one type of materialmore suitable than another type for a particular application.

The term oriented is thought to be well understood in the packaging artand refers to a material which has been specially processed to obtain ahigh degree of molecular orientation which imparts the requisite shrinkcharacteristics to the material. Materials of this general type aredisclosed in United States Patents 2,385,257, 2,497,376, 2,650,213,2,668,403 and 2,762,720. Other types of suitable oriented heatshrinkable materials are also available and undoubtedly other types oforiented heat shrinkable materials suitable for use in my invention willbe subsequently developed.

In the presently preferred embodiment of my invention, I prefer to useoriented heat shrinkable polymer film and it has been my experience thatthin film is preferable. I have experimented with an oriented heatshrinkable rubber hydrochloride polymer film material known as Snug- Pakand sold by Tee-Pak, Inc. I have found that Snug- Pak material inthicknesses of about 1 mil or less produces exceptional results.

Since film material and sheet material are commonly distinguished in thepackaging industry by thickness, it is my intention to adopt thedistinction specified for the packaging industry in Modern PackagingEncyclopedia of 3 mils or less for film material with sheet materialbeing thicker than 3 mils.

Furthermore, it has been my experience that fragile film is generallypreferable and has the distinct advantages of, among others, being morereadily conformable to the shape of the container and more easily openedon the container. Some fragile films are unable to sustain themselves ina horizontal plane under their own weight and, hence, unsupportedportions of such film extending beyond the rim of a container will drapedownwardly around the sides of the container without the necessity ofapplying forces sufficient to permanently deform the material. The termfragile is thought to be well recognized in the packaging industry andis generally related to the property of stiffness which is anexponential function of the thickness of any given material as well asthe inherent physical properties of the material. Sometimes thisproperty is also discussed in terms of limpness. A strong tough stiffmaterial such as polyethylene terephthalate must be extremely thin inorder to be anyway near as fragile as substantially thicker films ofother materials such as, for example, polyvinylidene chloride or rubberhydrochloride. The quality of fragility or stiffness may be demonstratedby comparing 2 mil and /2 mil polyethylene terephthalate film material.It will be readily seen that the 2 mil material is far more rigid andstiff than the /2 mil material.

The aforementioned objects, and others, have been attained byutilization of the inventive principles incorporated in the illustrativeembodiments of the invention shown on the accompanying drawing whereinzFIGURE 1 is a cross-sectional view of closure materials for amultiple-part closure in an initial stage of manufacture;

FIGURE 2 is a side elevational view of the closure materials shown inFIGURE 1 in a subsequent stage of manufacture;

FIGURE 3 is a cross-sectional view of closure materials for another typeof multiple part closure on a container prior to shrinkage thereon;

FIGURE 4 is a cross-sectional view of another arrangement of closurematerials for the other type of multiple part closure mounted on acontainer prior to heat shrink- FIGURE 5 is a cross-sectional view ofanother arrangement of closure materials for the other type of multiplepart closure mounted on a container prior to heat shrink- FIGURE 6 is across-sectional view of another arrangement of closure materials for theother type of multiple part closure mounted on a container prior to heatshrink- FIGURE 7 is a cross-sectional view of another arrangement ofclosure forming materials mounted across the mouth of a container;

FIGURE 7a is a cross-sectional view of another arrangement of closureforming materials representing a 6 subsequent rearrangement of theclosure forming mate rials shown in FIGURE 7. i

FIGURE 8 is a cross-sectional view of a different arrangement of closureforming materials on a container;

' FIGURE 8a 'is a partial cross-sectional view of a rearrangement of theclosure forming materials shown in FIGURE 8 in association with thecontainer rim;

FIGURE 9 is a cross-sectional view of a formed closure having associatedclosure opening means in position on a container after heat shrinkage;

FIGURE 10 is a cross-sectional view of a formed closure havingadditional sealing means associated therewith on a container after heatshrinkage;

FIGURE 11 is a cross-sectional view of a portion of apparatus forassociating closure forming materials as shown in FIGURE 1 prior toapplication to a container and heat shrinkage thereon;

FIGURE 11a is a cross-sectional view, with parts removed, of apparatusfor applying closure materials to a container and for applying heat toform the closure on the container by heat shrinkage;

FIGURE 12 is a cross-sectional View of a portion of another type ofapparatus for positioning closure forming materials on a container andfor applying heat to form the closure on the container by heatshrinkage;

FIGURE 13 is a cross-sectional view of a portion of still another typeof apparatus for positioning closure materials on a container andapplying heat for shrinkage;

FIGURE 14 is a perspective view of a closure for a container having aninspection window for viewing the contents of the container;

FIGURE 15 is a diagrammatic illustration of apparatus for associatingclosure materials with a container;

FIGURE 16 is a perspective view of a closure with attached stiffeningmeans on a container;

' FIGURE 17 is a side elevational view, partly in section, of anotherclosure with attached stiffening means; and

FIGURE 18 is a partial sectional view of the apparatus shown in FIGURE11.

THE CLOSURES AND CLOSURE MATERIAL ARRANGEMENTS It will be perceived thatthe inventive principles are susceptible of incorporation in a varietyof closure forms. The illustrative embodiments of the invention shown inthe drawings may be divided into three basic closure types which are:

(l) A closure formed from a combination of separate closure materialswhich are partially secured together and when shrunk form a singleclosure device;

(2) A closure formed from a combination of closure materials which arecompletely separate from one another and when shrunk form a multi-partclosure; and

(3) A closure formed by heat shrinkage of a single piece of unformedoriented heat shrinkable film material alone.

Multiple part closure with peripherally joined lay'ers In the multiplepart closures, the inner or underside cover material may be made from aclear, translucent, or opaque oriented heat shrinkable film of any ofthe various polymer materials. The outer cover material may also be ashrinkable material or, preferably, a moldable rigid or semi-rigidmaterial such as aluminum, paper, plastic, glass, steel, etc. Thepurpose of the inner material is to form a closure and provide a sealfor the container on which the closure is used. The purpose of the outercover is to provide a mold or retaining device and shield for the innermaterial during the formation of the closure by heat shrinkage and tosubsequently provide a protecting outer cover for the inner closure.

Referring now particularly to FIGURES 1, 2 and 11, there is shown anarrangement of separate closure materials for forming a multiple-partclosure having the various parts partially joined solely along the rimand apparatus for associating the closure materials. In the illustrativetwo-part closure example, an outer layer 1 of closurematerial and aseparate inner layer of oriented heat shrinkable polymer film closurematerial are associated in face to face relationship as shown. The innerlayer 5 of closure material is provided to obtain a seal across themouth of the container while the outer layer 1 of closure material isprovided for protective purposes, i.e., to prevent damage to the innersealing layer 5. Both layers of closure material may be made from thesame material or the inner component may be made from heat shrinkableoriented plastic film and the outer material may be made from asemi-rigid moldable material.

The peripheral portions of the closure materials extend substantiallytransversely to the central portions of the closure materials to form askirt portion having vertically extending pleats 4 and a beaded andexpansible rim 3 at the bottom of the skirt portion. The bulgedappearance shown in FIGURE 2 is achieved by applying pressure to thecentral portions so that the skirt portion in the area of the crease 2,formed in the skirt area of the outer layer 1 of closure material inspaced relationship above the more or less loosely rolled edge 3 at therim, is outwardly displaced.

The connection of the materials to one another may take place prior toor during association of the closure materials with the container. Inthe embodiment shown in FIGURES 1, 2, 11 and 11a, the closure materialsare rolled, curled, bent or otherwise temporarily or permanently heldtogether so that the inner closure material is held or retained by orwithin the outer closure material. The securing together of the closurematerials is done prior to, during, or after the association of thematerials with the container. The closure materials may be associatedprior to application to the container by apparatus of the type shown inFIGURE 11. The difference between formed and unformed material isclearly illustrated by reference to FIGURES 1 and 11. In FIGURE 11,formation of the crease 18 is shown to require similar displacement ofthe inner thin fragile film 5. However, as shown in FIGURE 1, only therelatively rigid and stiff outer cover 1 is permanently deformed whereasthe inner layer 5 of thin fragile film does not have a correspondingcrease and was, therefore, not formed.

FIGURE 18 illustrates the details of the male forming die 15 whichcomprises a pressure member 15a and a head member 15b normally separatedby springs 38. In operation, the springs are compressed and theresilient member 16 being restrained on three sides, is forced outwardlyagainst the female die in the general area of the groove of the femaledie. Thus a peripheral crease is formed in the side wall of the outerlayer of closure material. It will be apparent that in a multiple partclosure of the type shown in FIGURES 1 and 2, the innermost layer ofclosure material is free to move independently of the outer layer ofclosure material except at the rim areas which provide the only point ofphysical attachment.

The closure materials are thus associated in a form having, as oneexample, a circular top portion and an integral peripheral flange with abeaded rim. This type of device may 'be snapped onto a container withthe beaded edge locked circumferentially below the rim of the container.

Since the rim of the inner material is rolled into the rim of the outermaterial, the two separate closure materials are locked and retainedonly at the rim area. If preferred, additionally, or alternately, theclosure materials may be bonded or glued to one another peripherallyalong the rim. This arrangement of closure materials has a beaded andexpansible rim which may be snapped onto the rim of an aluminumcontainer or the like.

Since the more or less loose roll or double fold in the rim area and theadjacent skirt portions are pleated, the associated closure materialsare freely able to expand and contract as they are applied over themouth of' the container. Expansibility and contractibility of the-rimportion both subsequent and prior to the formation of the closure by theapplication of heat is facilitated by: the pleats 4 which are formed inthe skirt portion of the closure materials as the skirt portions arepositioned downwardly relative to the center portions. The loose roll orfold in the rim may involve a plurality of complete turns rather thanone as shown. In order to facilitate association of the closurematerials in the rim area, it is desirable that a thin plastic filmmaterial be utilized which is relatively fragile and permits easymanipulation.

Consequently, when heat is applied to the rim of the closure materialsor to the container-closure material assembly, the inner layer of filmwill primarily shrink a maximum distance circumferentially around therim of the container due to more rapid heat absorption at the exposed,uncovered, and unshielded skirt portion of the film. The beaded rim willshrink circumferentially and be pulled tighter around the container.Since both elements are engaged at the rim area, the outer material willalso be more tightly secured on the container. The film will be shrunkalong the rim to conform to the shape and irregularities of thecontainer rim creating an additional seal around the rim of thecontainer. Due to the primary local shrinkage around the rim of thecontainer, the entire piece of inner closure material is elasticallyfastened or anchored at the rim of the container and the remainder ofthe film is pulled tightly across the mouth of the container.Consequently, the inner closure material is in constant tensionresulting in further tightening and improvement of the seal at the edgeof the container.

Heat is applied to eifect selective shrinkage of the cover with theplastic film material shrinking a maximum amount circumferentiallyaround the rim of the container due to the cover design. The closurematerials will form a closure having the shape and configuration of therim of the circular, rectangular, or other shape of the container.Furthermore, a leakproof seal will be created around the rim of thecontainer.

Other types of multiple part closures connected to one another solely atthe rim areas are shown in FIGURES 7, 7a, 8 and 80. FIGURE 7 illustratesan inner plastic film closure material 5 and an outer protective closurematerial 10 placed over a container 9 with a beaded rim. Subsequently,these closure materials are associated, to make a tight closure as shownin FIGURE 70. Obviously, if both materials are heat shrinkable, they maybe associated by simultaneous heat shrinkage. Alternatively, thematerials may be associated by a rolling operation prior to shrinkage.Then heat is applied to cause selective shrinkage around the rim. FIGURE8 shows a straight edge container 12 having an inner closure material 5associated with a recessed outer closure material 11 which is appliedover the top of the inside closure material. Subsequently, as shown inFIGURE 8a, both layers of closure material and the container rim arerolled together and subjected to a subsequent heat sealing operation.

Multiple part closure with completely separate layers Referring now toFIGURES 3-6, various formspf multiple part closures are shown in whichthe ditferent closure materials are completely separate from oneanother. The innermost layer of closure material ismade of oriented heatshrinkable polymer film material. The outermost layer of closurematerial may be made from mold-v of closure material and placement onthe container. Con sequently, the preformed outer cover serves as a moldor retaining device and shield for the inner layer of unformed closurematerial during heat shrinkage to form the closure, and thensubsequently serves as a protecting cover for the inner cover.Consequently, a multiple part closure having an elastic periphery isprovided which permits separate removal and replacement of the outercover and the inner cover whereby inspection of the contents of thecontainer may be made without breaking the seal of the inner component.

In FIGURES 36, the inner layer of closure material 5 may be held on thecontainer by various typesof outer covers. In FIGURE 4, a single layercover 1, which may be preformed as previously disclosed by reference toFIG- URES l, 2 and 11, is shown holding the inner layer of unformedoriented heat shrinkable polymer film across the mouth of the containerwith pressure being exerted on the rim to hold the film in place. Theskirt portion of the film is pleated as previously illustrated in FIGURE1 and is loosely downwardly draped below the container rim as shown. 7

Similarly, in FIGURES 4-6, preformed outer covers 6, 7, 8 hold theunformed inner layer of closure forming material 5 on the rim of thecontainer prior to heat shrinkage.

In an arrangement of closure materials as previously described, theheat-shrinkable film protrudes beyond the rim of the container and isheld in place on the container by a retaining and shielding snap-oncover. When the container-cover-film combination is subjected toover-all heat, it will be seen that the protruding exposed andunshielded portions of the film will be heated first since the otherportions of the film are shielded from the heat. Consequently, theexposed skirt portion will shrink first, i.e., before the rest of thefilm which is shielded by the outer cover and the container, so thatselective shrinkage is effected. A removable and reappliable closurehaving an elastic edge is thus formed.

Again, particularly advantageous results are attained by using fragilethin film on the order of 1 mil for the inner component.

One-piece closure It is also a novel feature of this invention to placea piece of unformed oriented heat shrinkable film on top of a paper,plastic, aluminum sheet or foil container; to retain and shield it bymeans of any outer cover; and, by subjecting it selectively to heat, toshrink it around the mouth of the container thereby forming a leakproof,dome-shaped, removable and reappliable cover.

In other words, the oriented heat shrinkable film may be used alone tosimultaneously form a one-piece closure on a container and seal thecontainer by application of heat to cause shrinkage. It will beperceived that the inner component of a multiple part closure withcompletely separate layers is in fact a one-piece closure of the typenow being referred to. FIGURES 9 and 10 show a formed one-piece'closureon a container, the pleated skirt portion ofthe oriented heat shrinkablefilm material having been shrunk inwardly onto and around the containerrim and the sidewall.

It is, therefore, clearly apparent that I have invented a new andimproved closure which is extremely sanitary in use and which willdecrease thequantity of container material required to pack a certainamount of goods. The reduction in container. size is made possiblebecause of the fact that the presentclosure extends across the top ofthe container without extending therein. In prior art devices of theordinary inside friction type, the closures are sealed on an inwardlyextending rib located beneath the top of the container. Consequently,approximately 8% of the normal capacity of the container is oftenwasted. By'utilizing a flexible transparent film across the very top ofthe container the entire container may be utilized. Such an advantage isparticularly applicable in aluminum packaging which is'becoming socommon to day.

- Closure with, tear means Referring again to FIGURE 9, the single piececlosure 5 is shown to have an opening string located beneath it andextending over the rim of the container downwardly beyond the peripheraledge of the closure. Any of the covers may have a means of tearing orotherwise removing the seal film cover incorporated therewith. A string,band, etc. 13 may be incorporated into the cover construction prior toor during the sealing operation.

Closure with additional sealing means FIGURE 10 shows a one-piececlosure 5 with additional sealing cement, wax, or other bonding media 14located at various spots, or continuously, around the edge of theclosure or container. The sealing cement may be applied to the otherconstructions.

It will be understood that the additional sealing means is not generallynecessary, but if desired, it will adhere to the shrinking or shrunkenfilm during the heat sealing operation and thereby provide doubleprotection against leakage. A properly selected wax, heat sensitivecement, or heat softening material, can be applied so that, when heat isapplied, the wax will melt simultaneously with the shrinking of thefilm, the film enveloping the rim of the container and the melting waxbeing drawn by capillary action into any surface irregularities at therim of the container to therewith form or assist in form- 'ing aleakproof seal.

Closure with window Referring now to FIGURE 14, a multiple part closurecomprising an inner layer of transparent oriented heat shrinkable filmand an outer protective cover having a viewing window is shown.Consequently, the outer cover 30 is provided with a hole 31 in thecenter for visual inspection through the transparent inner cover 5. Theability to use transparent closures facilitates merchandising offoodstuffs because the public is able to see the contents of thepackages.

Closure with attached stifiening means Another object of this inventionis to provide a twopart or three-part closure comprising an innerstifiening component attached to an outer sealing closure component withor without a further protective covering for the sealing closurecomponent. The use of a stiffening component will reduce the cost ofmanufacture of the container by reducing the amount of containermaterial required.

FIGURES 16 and 17 show closures having stiffening elements which areused to reinforce the rim of the container with which the closures areassociated. In these modifications, an oriented heat shrinkable polymerfilm closure material is provided with an integrally attached innerlayer of stiffener material comprising a moldable or rigid material suchas cardboard or plastic which may be suitably attached to the heatshrinkable film. The inner stiffening member 40 is designed to fitinside the container rim, as for example in FIGURE 16, and when heat isapplied the closure material 39 will shrink around the rim of thecontainer 41 as previously described to form a sealing closure. Thecardboard, plastic, etc., inner layer will act as a stiffener or bracefor both the closure 39 and the container 41. Such an arrangement is ofparticular advantage on oblong containers where the long side of thecontainer rim and adjacent side wall may tend to buckle under thetension of the shrink film. In such cases, the stiffener will preventdeformation of the container. The reinforcement 43 may lie over the rimof the container 44 as shown in FIGURE 17 in which case it will stiffenonly the plastic closure 42 and not the container proper. The stiifenersmay be shaped in the form of a single rib, cross, disk, or any othersuitable configuration. Obviously, additional layers of closure materialmay be provided to obtain an outer protective cover if desired.

METHODS OF MANUFACTURING THE CLOSURES Applying the unformed closurematerial One of the major advantages of the present invention is thatthe unformed closure material may be purchased from the manufacturer inrolls of basic raw sheet form material as indicated at 34, 36 in FIGURE15 and directly applied to the container without any subsequent formingoperations except for severance of suitable lengths of the material bysevering apparatus 37.'If a one-piece closure of the type shown inFIGURE 12 is to be formed, only a single length of material 33 will bebrought into position above the container 32. If a multiple piececlosure is to be formed, then one or more additional lengths of material35 may also be simultaneously positioned across the top of the container32.

One or more of the severed lengths of material 33, 35 are located acrossthe open mouth of the container with the peripheral portions whichextend beyond the container rim positioned downwardly around the sidesof the container to provide a peripheral skirt portion. The amount ofdrape and ease of positioning, obviously, is dependent upon thestiffness of the material. I prefer to use a material which issufiiciently fragile so as to permit the material to relatively easilyacquire a draped pleated condition around the rim of the container. Ifthe material is sufficiently fragile it may have considerable drapesolely by reason of its own weight under the influence of gravity.Furthermore, the material may also be blown downwardly inwardly by thedynamic application of hot air for shrinkage. Actually, it may not beabsolutely necessary that a draped condition be obtained in everyapplication, but a thin fragile material does facilitate subsequentformation of the closure and lends itself to high speed productionmethods.

Holding and shielding the unformed closure material An alternativemethod of holding closure material on a container rim is illustrated inFIGURE 12 wherein a piece of limp, fragile, thin film made from asuitable oriented heat shrinkable polymer material is positioned on acontainer having a beaded rim portion and held and shielded by dieapparatus 23. The unformed film material is sufliciently limp andfragile so as to easily acquire the position shown when located on thecontainer without aplication of any force resulting in permanentdeformation of the film material. In other words, if the die 23 wereremoved, the film material could be removed from the container and wouldbe exactly the same as it was before it was positioned on the containerwithout having suffered any permanent deformation whatsoever. Theunformed film material, when associated with a container, includes acentral portion extending across the mouth of the container and a skirtportion which extends downwardly around the sides of the container.

.If a piece of unformed film material, such as the piece of film shownin FIGURE 12, is positioned across the mouth of a container with theperipheral portion extending downwardly to form a skirt, the skirtportion will be arranged in a plurality of pleats 4 similar to thearrangement shown in FIGURE 1 whereat a piece of film 5 hassubstantially the same configuration. In other words, when a piece offilm is arranged to provide a skirt portion without permanentdeformation or shrinkage, that skirt portion of necessity must bearranged in pleats around the container. I

It will be readily appreciated that the-holdingand shielding functionperformed by the apparatus shown in FIG- URES 12 and 13 can equally wellbe performed by an outer closure in combination with an inner closure ofunformed oriented heat shrinkable polymer film material. For example, inthe arrangements of FIGURES 3-6, a two-part closure is shownin whichunformed oriented heat shrinkable closure material 5 is held oncontainers by an outer layer of formed closure material and is shieldedthereby. The skirt portion of the unformed film hangs downwardly withoutpermanent deformation until heat is applied for shrinkage. When the heatis applied, only the exposed portions of the skirt portion of the filmare directly exposed thereto and the central portion of the film is heldon the container rim and shielded by the outer cover.Consequently,'selective shrinkage is attained. It may be noted that thecentral portion of the oriented heat shrinkable closure material isloosely positioned relative to the outer closure material so that theinner closure material may be stretched tautly across the mouth of thecontainer regardless of the position of the outer closure material. 1

Similarly, the holding and shielding function is also provided by theouter cover in a two-part arrangement comprising a plurality of layersof separate closure materials joined solely at their peripheries, asshown in FIGURES l and 2. The central portions of the inner closurematerials, which are only loosely associated so that the inner orientedheat shrinkable polymer material may move relative to the outer materialto establish the desired sealing condition around the rim of thecontainer, are shielded by the outer cover and the skirt portions areexposed.

Applying the heat for shrinkage The heat may be selectively appliedtothe exposed portions of the skirt, which may be a narrow band of theskirt as shown in FIG. 3 or 11A or the entire skirt as shown in FIG. 12,of the closure material by any suitable means such as the heatapplication means 27 shown in FIGURE 13, the heat application means 25shown in FIGURE 12, or the heat application means 23a shown in FIGURE11a. The heat may also be applied by any other suitable means such as bythe creation of a suitable high temperature ambient condition having atemperature surficiently high to cause heat shrinkage of the exposedportions of the oriented heat shrinkable polymer material. Although theapplication of heat by convection through a fluid medium is preferred,any heat means such as hot air, hot water, steam, electricity, or eveiianopen flame may be used in some applications.

Selective shrinkage By applying the heat selectively to the skirtportion of the oriented heat shrinkable polymer'film material, whileholding the top portion of the film on the rim of the container andshielding the top portion, theskirt'portion is caused to shrink firstand to a'greater extent inwardly against the container around the rimportion while bringing the portion of the film material on the rim "intoextremely close surface to surface engagement with the container rim.Subsequently, the centenportion of the closure material may be subjectto'an application of heat to cause further shrinkage of the centerportion resulting in tightening thereof and'in drawing the film materialinto tight sealing engagement around theentire periphery of thecontainer; In this manner, a t'autclosure having an extremely pleasingappearance may be manufactured.

In any event, the essential conditions for selective shrinkage on anopen mouth; under-stu l"fed container are that the film be held onthe.container rim substantially fiat across the mouth ofthe containerwhile the edge of the'film is arranged around the rim of the containerin pleats. When heat is applied to the rim area of the container the'protruding film will shrink and will conform tdthe shape of the rimofthe container. Hence, a tight sealds formed around the rim'while theremainder of therim is pulled'tightly across the'mouth of the containeror the contents'therein. If additional heat is subsequently applied overthe entire area of the closure further'tightening of the closurematerial will result and the seal will be improved. Such'a method hasthe advantage that the outer covers, in the case of a two-part closure,can be rer'noved'without disturbingthe seal of the film portion of theclosure. Furthermore, the outer cover can be repeatedly taken E andsnapped back onto the container without losing its original tightnessand tension due to' the expandible pleated rim. Therefore, theconcept'of selective shrinkage of shrinkable film or the like may bedefined as the controlled reduction in size of portions of the film to asubstantial degree while holding the reduction in size of the balance ofthe film to a lesser degree or to none at all. Such a concept applies toall of the closures hereinbefore described by reason of the fact thatsufiicient shrinkage of the film at the rim of the containers is firstobtained to form the closure and provide a seal at the mouth of thecontainer While controlling shrinkage across the mouth of the containerthrough the retention of the film at the rim and by shielding or thelike.

Closure tension and elasticity One of the objects of my invention is tomake an improved closure in which the rim is pleated before being formedin such a manner that elastic expansion and contraction at the rim areamay occur to enable the closure to be applied to and removed from acontainer whereon the closure is held by locking the rim of the closurebelow a slightly larger bead on the mouth of the container.

Another object of my invention is to provide a closure which will'accept, respond, and reshape itself to conform to deforming force'supon the container, closure, or upon both, :withoutdamage to or loss ofthe seal original- 1y obtained. V

One of'the advantages of :the present invention is that a piece oforiented heat shrinkable polymer material which'has heat selectivelyapplied to a pleated skirt portion will have sufiicient elasticity andresilience to permit'the closure, formed by the application of heat tocauseshrinkage, to be removed from and reapplied to the rim of acontainer. Such a closure will deform due to reduced or increasedpressures without damage to or loss of seal thereby reducing' the hazardof deformation or breakage of the container due to varied pressures.Such a closure will also materially strengthen the container upon whichit is utilized by resisting deformation and shock.

Closures embodyin g a heat shrinkable material as heretofore describedwill impart added strength and rigidity to the container, closure, andseal by utilizing physical forces that are developed by shrinkage of thefilm. The film, upon being tightened during shrinkage, is in a state oftension. Insuch a condition, active radial compressive forcesare createdupon the rim of the container which cause reactive expansive outwardforces. A stable equilibrium is established between these forces and inconsequence whereof added rigidity is imparted to the closure, thecontainer, and the seal. I

Therefore, "a disclosure made in accordance with the principles of thepresent invention creates a seal that permits a 'wider degreeofjcrushing or deformation of the container than heretofore permissiblewith other closures. This is' evidenced by the fact that a crushingaction on the container closure arrangement is accompanied by acorresponding contraction in the shrunken film material due to inherenttension which tends to reduce the size of the film at any and all timeswhen the restraining force provided by the rim is reduced or relaxed.Thus, changes in shape of the rim may be accommodated without damage tothe seal originally effected. It will also be apparent that a closureincluding a layer of outer protective closure material further protectsthe seal and, even though the outer layer may be damaged, the seal willremain intact. Such an advantage is obtained because the inner layer offilm closure material is free to move independently of the other layers.

Thus the closure tends to retain its effectiveness despite abuse whichcauses deformation of the container and the cover, or changes inpressure due to changes in temperature of the food or other contents, orchanges in atmospheric pressure due to the mode of shipment or storage(air transportation used by military forces in the tropics or polarregions, etc.).

Closure for frozen goods The present invention is particularly wellsuited for packaging of frozen foods. A single layer of oriented heatshrinkable polymer film material may be utilized to form the closure ona container of frozen goods, the frozen goods being utilized to maintainthe central portion of the closure material at a reduced temperaturerelative to the rim portion so that selective shrinkage is attained.

For example, in forming a closure on containers containing frozen foods,the seal may be made by passing the container covered by the closurematerial through a heated oven. The container and central portion of theclosure material will be at a lower temperature due to the frozencontents and a greater amount of time and/ or heat will be required forthe central portion to reach the shrinkage temperature. The rim area,which is capable of most rapid heat absorption, will reach the shrinkagetemperature first.

APPARATUS Referring now to FIGURES 11, 11a, 12, 13, 15 and 18, apparatuswhich may be used in making the aforedescribed closures is illustrated.

FIGURE 11 shows a male die 15 (illustrated in greater detail in FIG. 18)having a resilient ring 16 located therein. A female die 17 has a groove18 located opposite the resilient ring 16 in the male die. When pressureis applied by the male, or forcing die, the closure material 1 beingformed is forced into the groove by means of the elasticity of theresilient material to form a crease. Although the closure material 5 isalso laterally displaced, a permanent crease is not formed in it asshown in FIGURE 1. At the same time, curling rings 19, 20 roll theclosure materials at the rim. The resilient ring 16 may be omitted ifdesired, but then a less pronounced crease will be formed.

FIGURE 1.2 shows a type of suction sealing disk or head 23, having filmholding suction and positioning lines 24 in it. Suitable means are ofcourse provided to support the container and to move the head 23 intoposition on the containers such as shown, for example, in US. Patent No.2,732,116. FIGURE 12 shows only a shrinkable film placed over thecontainer for forming and sealing thereon by means of hot air or steampassing through apertures 25 simultaneously or separately. Hot air maybe applied through the apertures at the side first and then through theaperture at the top or in certain cases the hot air may be appliedthrough the side and at the top simultaneously. Obviously, any numberand spacing of holes through which the hot air is applied may be usedaround the sides and around the top. The sealing head or disk is equallyapplicable for use with the multi-part type closures.

FIGURE 13 shows another type of sealing device 26 having hot airapertures 27 therein and utilizing a hold down plate 28 to hold theclosure material in place on the container rim and to provide a shieldfor the central portion.

FIGURE 15 shows rolls of basic raw sheet material 34, 36 which maybedirectly applied singularly or in 15 combination to the container 32,the container being used as the male forming component of the closure.

If two strips of material 33, 35 are being used, the roll 36 wouldrepresent outer protective material 35 and the roll 34 would representinner transparent thin oriented heat shrinkable polymer film 33. Thecontainer 32, of course, can be of any shape, circular or rectangular,for example, and is illustratively shown to have straight nonbeadedsides although containers with beaded rim portions are equally wellapplicable. A shear 37 is provided to cut the layers of material. Ifdesired, a suitable heat sealing device, for example as shown in FIGURE13, may be cooperatively associated with the shears so as to provide aone motion operation for sealing a container from basic sheet material.When making a multiple part closure the closure materials may beassociated by rolling them into a single roll by a prior operation.

THE CLOSURE MATERIAL My invention is particularly applicable withoriented heat shrinkable polymer films which are normally less than 2mils (.002) thick and capable of large shrinkage in all directionsparallel to the film surface. Actually, thin films in the range of .0002(20 gauge) to .0008" (80 gauge) are generally most satisfactory. Theexact thickness of the film will depend somewhat upon the area and goodsto be covered. Where a fragile film is required the stronger materialssuch as nylon should not exceed about 1 mil in thickness.

It is within the scope of my invention to use a biaxially oriented filmas well as a film that is shrinkable in only one direction and may haveparticular utility on containers of particular form such as onrectangular containers.

Examples of certain films which may be used are oriented films of rubberhydrochloride (oriented Pliofilm such as Snug-Pak) or vinylidenechloride (oriented Saran or Cryovac film.) Such films are heatshrinkable by reason of their oriented internal structure. Orientationis commonly induced by stretching the film unidirectionally ormultidirectionally while heated or super cooled. The orienting of suchfilm is conventionally done by mechanical, pneumatic or other physicalmethods of expanding or stretching the films and may also be done bychemical, electrical or other means for realigning the molecularstructure.

By way of example, especially good seals may be obtained on containershaving circularly shaped mouths by the use of oriented heat shrinkableplastic film material capable of linear shrinkage of 50% in alldirections parallel to the film surfaces. Such films shrink attemperatures of approximately between 160 and 220 Fahrenheit. One typeof such material is the commercially available Snug- Pak of 40, 50 and60 gauge as sold by Tee-Pak, Inc. This film is stretched to twice itswidth and to twice its length whereby the area is quadrupled andsubsequent shrinkage results in a reduction of approximately A of theoriginal stretched area. Pliofilm made by Goodyear Tire and RubberCompany, for example, may be stretched appreciably more or appreciablyless and consequently will be capable of shrinking more or less thanstandard Snug-Pak. The percentages of shrinkage in temperatures givenare by way of illustration only and may be varied within wide limits.Obviously, the shrinkage temperature may also be varied for differentheat shrinkable films. However, in all or practically all of the knownoriented films, the shrink action will take place instantaneously oralmost instaneously.

Films possessing the above-mentioned overall shrinkage properties aredesirable in many instances in order to produce adequate tightness ofseal at the rim of the container where the greatest degree ofutilization of the shrinkage property is required. It is to beunderstood, however, that the shrinkage values do not represent theoverall reduction in size of the entire film in the closure after heatapplication, nor the actual shrinkage required to produce the seal.

The selection of films of suitable shrinkability, suitable shrinkagetemperature, and suitable strength 'will be dictated primarily by thenature of the container or the contents and the temperatures to whichthe local area may be heated at the time the closure is to be formed.

While I have referred to the film as being transparent, since thatquality would be most desirable in the food packaging field, it is ofcourse understood that a translucent, opaque, or colored film might alsobe used. A film may be colored by integral association of a suitablecoloring medium or the coloring may be separately applied to one or bothof the side surfaces of the film. Also the film may be a single film ora laminated film of two or more plies of material which are integrallyassociated throughout their length in permanent surface to surfaceengagement. The principal requirement in a laminated integrallyassociated closure material is that at least one of the plies of thematerial be heat shrinkable and that the heat shrinkable ply control theoverall action of the laminated material.

The invention claimed is:

1. A closure for a container comprising a piece of partially heatshrinkable thin film material, a central portion of said piece ofmaterial having a first shrinkable condition and adapted to extend overthe open mouth of the container, and a rim portion of said piece ofmaterial having a second shrinkable condition and adapted to extend overthe rim of the container and hold the closure on the container, saidcentral portion being more shrinkable than said rim portion.

2. The invention as defined in claim 1 and wherein said rim portioncomprises a pleated skirt extending downwardly on the rim of thecontainer and terminating in an elastic edge.

3. The invention as defined in claim 1 and said closure having athickness on the order of 1 mil.

4. The invention as defined in claim 1 and having a separate outerprotective cover associated therewith, said outer protective coverhaving an expansible and contractible rim of a size for snap-onassociation with said container, and said outer protective cover beingremovable from and reappliable to said container and wherein saidclosure is made of transparent plastic material and said cover having aviewing window centrally located thereon.

5. The invention as defined in claim 1 and having a separate outerprotective cover associated therewith, said outer protective coverhaving an expansible and contractible rim of a size for snap-onassociation with said container, .and said outer protective cover beingremovable from and reappliable to said container and wherein said outerprotective cover is joined to said closure solely at the rim.

6. A closure as claimed in claim. 1, provided with a cement adjacent therim of the receptacle circumferentially for additional sealingefficiency.

7. A closure as claimed in claim 1, provided with a heat softeningmaterial adjacent the rim of the closure, said heat softening materialcapable of softening immediately prior to or simultaneously with theshrinking of the film during heat application, said heat softeningmaterial flowing or, being drawn by capillary action into any existingirregularities in the surface of the rim of the conltainer, and therebyassisting in creating a leakproof sea 8. A closure having a centralportion and a skirt for containers made of a heat shrinkable plasticmaterial, said closure being relatively thin and ina heat shrinkablecondition over the major area of the central portion thereof, saidclosure terminating in a substantially unshrinkable skirt which, when inclosing relation with a container, snugly fits the coextensive area ofthe container.

9. A container having a side wall and a cover forsaid container of abiaxiallyoriented film having high shrink 17 energy, said cover beingrelatively thin and in a heat shrinkable condition over the major areathereof, said cover terminating in a thickened and substantiallyunshrinkable sealing bead around the upper periphery of the side wall ofthe container.

10. A closure for receptacles, comprising a flexible, moldable materialin combination with a shrinkable film both face to face and drawn intoshape to form said closure, the shrinkable film being on the inside ofthe closure, said closure having a beaded rim and a pleated sidewall,said sidewall forming a peripheral bulge to receive the mouth of thereceptacle, said film portion of the closure being bonded around itsperiphery to the flexible, moldable material and being beaded togetherwith said material, said beaded portion and sidewall portion of the filmbeing capable of shrinking around the mouth of the container when heatis applied at the circumference of either the rim of the closure or themouth of the container, creating therewith a seal around the mouth ofthe container and tightening the rest of the film portion of the closureacross the mouth of the container when the film shrinks due to heat, andthe two parts of the closure being prevented from separating at the rimof the closure by the beaded portion of the closure the outer part beingprovided with a circular opening, said inner part being transparentwhereby the content of said receptacle may be viewed through saidopening and said inner transparent part of said closure.

References Cited UNITED STATES PATENTS 2,351,318 6/ 1944 Carew 229-43 X1,905,356 4/1933 West 215-38 2,119,901 6/ 1938 Beitler 226-80 2,331,79410/1943 Mallory 156-218 2,447,983 8/ 1948 Little 215-38 2,586,446 2/1952Stockburger 2l538 2,689,664 9/1954 Vingron 2l538 2,711,346 6/1955 Irwinet al. 29924 2,718,322 9/1955 Wilcox 2l538 2,754,959 7/1956 McCarty206-45 2,790,285 4/1957 Pike et al. 53-39 2,885,105 5/1959 Heyl et al.215-38 FOREIGN PATENTS 425,891 1/ 1947 Italy.

468,762 7/ 1937 Great Britain.

705,816 3/ 1954 Great Britain.

25 DONALD F. NORTON, Primary Examiner.

1. A CLOSURE FOR A CONTAINER COMPRISING A PIECE OF PARTIALLY HEATSHRINKABLE THIN FILM MATERIAL, A CENTRAL PORTION OF SAID PIECE OFMATERIAL HAVING A FIRST SHRINKABLE CONDITION AND ADAPTED TO EXTEND OVERTHE OPEN MOUTH OF THE CONTAINER, AND A RIM PORTION OF SAID PIECE OFMATERIAL HAVING A SECOND SHRINKABLE CONDITION AND ADAPTED TO EXTEND OVERTHE RIM OF THE CONTAINER AND HOLD THE CLOSURE ON THE CONTAINER, SAIDCENTRAL PORTION BEING MORE SHRINKABLE THAN SAID RIM PORTION.